Deepest Limits on Scattered Light Emission from the Epsilon Eridani Inner Debris Disk with HST/STIS

Abstract

Epsilon Eridani is one of the first debris disk systems detected by the Infrared Astronomical Satellite. However, the system has thus far eluded detection in scattered light with no components having been directly imaged. Its similarity to a relatively young solar system combined with its proximity makes it an excellent candidate to further our understanding of planetary system evolution. We present a set of coronagraphic images taken using the Space Telescope Imaging Spectrograph coronagraph on the Hubble Space Telescope at a small inner working angle to detect a predicted warm inner debris disk inside 1″. We used three different postprocessing approaches—nonnegative matrix factorization (NMF), Karhunen–Loève Image Processing (KLIP), and classical reference differential imaging, to best optimize reference star subtraction—and find that NMF performed the best overall while KLIP produced the absolute best contrast inside 1″. We present limits on scattered light from warm dust, with constraints on surface brightness at 6 mJy as−2 at our inner working angle of 0.″6. We also place a constraint of 0.5 mJy as−2 outside 1″, which gives us an upper limit on the brightness for outer disks and substellar companions. Finally, we calculated an upper limit on the dust albedo at ω < 0.487.